1. Field of the Invention
The present invention relates to a novel method to locally heat and isostatically press glass encapsulated materials at high pressures and at high localized temperatures. More specifically, the present invention relates to a method to compact a glass encapsulated powdered material at very high pressures having a localized heating element in the glass and localized temperature monitoring. In this way, the sample locally is heated, but the metal or ceramic pressure chambers are usually kept at low relative temperature of less than about 500.degree. C.
2. Description of Related Art
Powder technology using heat and pressure to form engineered materials and high performance articles is conventional. General aspects of the art include, for example, "Powder Metallurgy" by K. H. Roll in Kirk-Othmer: Encyclopedia of Chemical Technology, 3rd Ed., Vol. 19, pp. 28-62, John Wiley and Sons, New York, N.Y., published in 1982, and the references cited therein. Also see in the Kirk-Othmer volumes (3rd ed.): "High Temperature Alloys," by N. S. Stoloff, et al. (1980), Vol. 12, pp. 417-458; and "High Temperature Composites" by W. B. Hillig (1980), Vol. 12, pp. 459-481.
Superconducting materials are disclosed in "Superconducting Materials," by F. P. Missell, et al. in Kirk-Othmer: Encyclopedia of Chemical Technology, 3rd Ed., Vol. 22, pp. 298-331, published in 1983, and "Ceramics" is discussed by R. F. Davis, et al., in Kirk-Othmer: Encyclopedia of Chemical Technology, 3rd Ed., Vol. 5, pp. 237-314, published in 1979.
In U.S. Pat. No. 4,428,906, W. J. Rozmus discloses a number of features regarding the formation of an article from a powdered metal using heat and pressure.
Additional U.S. Patents of interest include:
______________________________________ 4,756,752 4,722,825 4,597,730 4,528,120 4,547,337 U.S. Re 31,355 4,656,002 4,596,694 4,227,927 4,744,943 4,738,610 4,524,138 4,732,556 4,724,123 4,657,822 4,632,793 4,041,123 4,490,319 ______________________________________
Specifically, E. E. Timm in U.S. Pat. No. 4,744,943 discloses a process for preparing dense consolidated bodies. The distinguishing feature of this process is to perform the process and immediately remove most or all of the fluid isostatic shell by pouring the hot assembly onto a screen and separating the fluid for recycle.
All of the references and patents described in this application are incorporated by reference in their entirety.
None of the references cited individually or collectively teach or suggest the present invention. It is therefore desirable to have a method to solidify and encapsulate materials at moderate and very high pressures using localized heating and localized temperature monitoring of the sample to be solidified without the need to heat the die or pressure pistons to temperatures which will deform them over time. The present invention provides such a method, which is less time consuming, less expensive, provides improved control of the process to compact the materials and the use of higher pressures and local temperatures than processes of the art.